arnie duncan, u.s. sackett of education, has generally been supportive of these value added numbers, after the data was published, the obama administration has provided financial incentives for states to provide value add educators for paying and promoting teachers. proopinion anyones point out they're a huge potential improvement over systems in which all teaches are paid in a system -- many experts warn these assessments have large margins of error and can deliver misleading results. the union representing the new york city teachers spent more than $100,000 on a up in advertising campaign, built around the headline, this is no way to rate a teacher. opponents argue the value added assessment creates a false impression used by parents and public officials who do not understand the limitations of of this. everybody is right up to a point. a man works extensively with value added data for teachers, warns that these are inharen day noisy. the results are based on a single test, taken on a single day, by a